The socialist political movement includes a set of political philosophies that originated in the revolutionary movements of the mid-to-late 18th century and of concern for the social problems that were associated with capitalism. [13] In addition to the debate over markets and planning, the varieties of socialism differ in their form of social ownership, how management is to be organised within productive institutions and the role of the state in constructing socialism. [2] [13] Core dichotomies include reformism versus revolutionary socialism and state socialism versus libertarian socialism . Socialist politics has been both centralist and decentralised; internationalist and nationalist in orientation; organised through political parties and opposed to party politics; at times overlapping with trade unions and at other times independent of — and critical of — unions; and present in both industrialised and developing countries. [29] While all tendencies of socialism consider themselves democratic, the term " democratic socialism " is often used to highlight its advocates' high value for democratic processes in the economy and democratic political systems , [30] usually to draw contrast to tendencies they may perceive to be undemocratic in their approach. Democratic socialism is frequently used to draw contrast to the political system of the Soviet Union , which critics argue operated in an authoritarian fashion. [31] [32] [33]